The inventive subject matter disclosed herein generally relates to units of small scale fibers suitable as fill materials in apparel items, sleeping bags, bedding, pillows, upholstery, cushions, and other such articles and uses. In some embodiments, the inventive subject matter relates to a fiber construct suitable for use as a fill material for insulation or padding, comprising: a primary fiber structure comprising a predetermined length of fiber; a secondary fiber structure, the secondary fiber structure comprising a plurality of short loops spaced along a length of the primary fiber. In some embodiments, the inventive subject matter relates to insulative fiber structures that mimic the structure and scale of natural down and thereby provide similar properties.
Various kinds of natural or synthetic filling material are known. Natural down, e.g. from waterfowl, is an excellent filling material having a number of outstanding properties. Down is the plumage that forms the undercoating of waterfowl (e.g., goose, duck or swan). It consists of tufts of light, fluffy filaments growing from one quill point, but without any quill shaft.
Among down's important physical properties is its loft, also known as fill power. Loft or fill is the volume occupied by a given unit of mass of material. Fill power is the most common parameter used to distinguish between different grades of goose down used in consumer products. A material with a higher fill power is able to occupy a greater volume with a smaller mass and in turn offers greater insulating capabilities. Because fill power has a strong influence on product value, strict guidelines and testing procedures exist to ensure that product labeling and performance concur. The
International Down and Feather Laboratory (IDFL) conducts much of the testing and ranking of raw down materials imported from around the world for sale in the United States. A piston-cylinder system is used to determine the fill power. The exact specifications and procedures for this test are available at the IDFL website (IDFL 2004). There are different standards for testing around the world; however, the interpretation and testing principles remain unchanged. For purposes of this patent specification, The International Down and Feather Bureau (IDFB) establishes testing methods and other standards for the international community, and all the IDFB standards and definitions as of Jan. 1, 2014, shall apply to this specification unless otherwise indicated herein.
(The standards and definitions are publicly accessible at the IDFB website, http://www.idfl.com/.)
The properties of down that make it so popular as an insulator are its lightweight, softness, compressibility, recovery power, resilience, and breathability.
Natural feather or down has, however, several disadvantages. For example, many steps are required for processing natural feather or down, since it is highly susceptible to damage by insects and microorganisms. Natural feather and down is also expensive, since it is available only in limited quantities. The handling and care of production animals may also raise animal welfare concerns. Further, down or feathers may induce an allergic reaction in some users. In wet conditions, down can become saturated with water. When this happens down loses its loft, compresses, and hence loses the great insulative properties because down is no longer able to trap air spaces for warmth. Because of this synthetic alternatives for down are constantly being sought. This and other problems have prompted research on novel fibrous materials to develop substitutes for natural feather or down.
Some prior art approaches to making down substitutes include various ways of bundling and bonding short fibers; forming fibers into spherical shapes; and flocking fibers by electrode position. In another approach, disclosed in U.S. Pat. No. 7,261,936, a down substitute in the form of fir-tree or dendritic structures is created from a multifilament fiber that is cut into short segments with fusion so that at one end of a unit filaments are fused together and at the other end they are free. In yet another approach, disclosed in EP 0620185, a down substitute has an elongate support structure with a generally dispersed array of discrete fine fibers, one end of the fine fibers being attached to the support structure and the other end of the fibers being free. However, no such prior art material is sufficiently comparable to natural down material in physical properties. The replication of natural down properties has been particularly challenging due to down's complex structure and physical properties.
FIGS. 1A and 1B schematically illustrate the general structure of a natural down cluster 1 (FIG. 1A). Down clusters may range from about 5 mm to about 70 mm in diameter. They have a central node or root with many strands 2 extending outwardly in all directions. The individual strands may be referred to as “primary” structures or fibers 3. A primary structure 3 has many fine structures extending outwardly along its length, which may be referred to as “secondary” structures or fibers 4. The primary structure 3 has a length of 3 mm to 33 mm, with typical lengths of about 14 mm to 20 mm. A natural down primary structure generally has from 50 to 1500 or thereabout secondary fibers 4 radially disposed along its length (FIG. 1B). With a length of 33 mm, and a spacing of 60 μm, gives 550 secondaries, or 1100 if you count each side separately. With a length of 3 mm, and a spacing of 60 μm, gives 50 secondaries, or 100, if you count each side separately. Natural down may also have one or two relatively short tertiary fibers (not shown) spaced along the length of and extending from each secondary fiber 4 per every 100 microns or thereabout.
Natural down's secondary structure lengths, which are indicated by “D” in the figures, generally, may range between 0.35 mm to 1.4 mm, with lengths of 0.55 mm to 0.75 mm being typical. The secondary fibers are highly resilient and resistant to permanent deformation, and they are capable of storing elastic energy. FIGS. 1A and 1B show representative dimensions of fibers, which can vary in nature.
In addition to the inherent challenges in replicating the physical structure of down, down substitutes are considered difficult to manufacture continuously at a low cost.
In view of the foregoing needs and disadvantages, there is a significant need for improved fill materials, particularly insulative materials that more closely replicate the properties of natural down and which are commercially feasible to produce.